Transformer



1957 E. J. ZELT ETAL TRANSFORMER Filed Jamv 26, 1953 Inventors: 1 Elmer -J. Zelt, Joseph 0. Hamilton,

Joy heir" Attorney.

United States Patent TRANSFORMER Elmer J. Zelt, Fort Wayne, Ind., and Joseph C. Hamilton, Chicago, 111., assignors to General Electric Company, a corporation of New York Application January 26, 1953, Serial No. 333,150

Claims. (Cl. 336-92) This invention relates to inductive devices such as transformers, and more particularly to devices of this type having an enclosing case.

In the design of small transformers and reactors, such as ballast transformers for fluorescent lighting installations, it is necessary to provide means for clamping the core laminations together, means for holding the core in the enclosing case, and means for grounding the coils and the core. In the past, separate elements have been provided for performing these several functions, thus complicating the assembly of the complete device and adding appreciably to the over-all cost. It is therefore desirable to provide a simple, inexpensive, and easily assembled arrangement for clamping the core, securing the core within the case, and grounding the coils and core.

It is therefore an object of this invention to provide an improved inductive device incorporating the desirable features set forth above.

Further objects and advantages of this invention will become apparent by reference to the following description and the accompanying drawing, and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In accordance with this invention, there is provided an inductive device having a laminated core with a coil positioned thereon. A clamping part, preferably formed of relatively thin sheet metal, is secured to one face of the core and has an indentation formed therein defining a socket with the core face. A case member encloses the core and has an opening formed therein, in which a connecting member, such as a self-tapping screw, is arranged extending into the socket and engaging the clamping part and core face thus securing the case to the core and grounding the core to the case. If it is desired that the coil also be grounded, one lead may be clamped between the clamping part and the core face.

In the drawing:

Fig. l is a view in perspective, partly broken away, illustrating a transformer having the improved construction of this invention; and

Fig. 2 is a fragmentary view further illustrating the improved construction of Fig. 1.

Referring now to the drawing, there is shown an inductive device, such as a fluorescent ballast transformer, generally identified as 1, having a core member 2 formed of a plurality of stacked laminations of magnetic material. The core 2 may have any conventional configuration well-known in the art and one or more coils, such as coil 3 may be positioned thereon.

In order to clamp the lamination of the core 2 together and to secure and ground the core 2 to a metal enclosing case 4, a plurality of clamping parts 5 are provided formed of relatively thin sheet material. Clamping parts 5 are respectively arranged abutting opposite faces of the core and are secured thereto thus clamping the laminations together in any suitable manner, as by rivets 6 which extend through suitable openings in the core. An indentation 7 is formed in each clamping part 5, intermediate its ends, thus defining a socket 8 with the face of the core 2. One or more small openings are formed in the enclosing case 4 and when the case is positioned on the core 2, these openings are respectively in registry with the sockets 8 formed by indentations 7 of clamping parts 5. Suitable connecting members, such as self-tapping screws 9, are arranged with their heads 10 abutting the exterior surface of case 4 and with their points 11 extending through the case opening and into the socket 8. The threads 12 of screws 11 engage the indentations 7 of clamping parts 5 and the face of core 2 thus securing the case 4 to the core 2 and grounding the core to the case.

If it is desired to ground coil 3 to the core 2, a pigtail lead 13 of the coil 3 may have its end clamped between a clamping part 5 and the face of core 2, as shown in Fig. 2.

It will now be readily seen that the threaded portion 11 of self-tapping screw 9 will have on the order of 50% of its threaded surface in contact with indentation 7 of clamping part 5 and that in addition, a substantial percentage of its threaded area will cut through any varnish treatment applied to the face of core 2 to contact the outer core lamination. It is thus seen that not only is the outer casing 4 firmly secured to the core 2, but also the core is well grounded to the case. It will be readily apparent that it may be desirable to utilize several of these connections, however, in the event that it is not necessary to utilize two screws on one side of the case, the bottom core clamping part may be a perfectly flat member rather than having the indented form shown in Fig. 1.

While we have shown and described a particular embodiment of this invention, further modifications and improvements will occur to those skilled in the art. We desire that it be understood, therefore, that this invention is not limited to the form shown and we intend in the appended claims to cover all modifications which do not depart from the spirit and scope of this invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An inductive device comprising a laminated core, a clamping part secured to one face of said core and having an indentation formed therein defining a socket with said core face, a case member enclosing said core and having an opening formed therein in registry with said socket, and a connecting member extending through said case member opening and into said socket in engagement with said indentation and said core face thereby securing said case member to said core.

2. An inductive device comprising a laminated core, a metal clamping part secured to one face of said core and having an indentation formed therein defining a socket with said core face, a metal case member enclosing said core and having an opening formed therein in registry with said socket, and a metal screw member extending through said case member opening and into said socket in engagement with said indentation and said core face thereby securing said case member to said core and grounding said core.

3. An inductive device comprising a laminated core, a clamping part formed of relatively thin sheet metal secured to one face of said core and having an indenta tion formed therein defining a socket with said core face, a metal case member enclosing said core and having an opening formed therein in registry with said socket, and a metal self-tapping screw arranged in said case member opening with its head abutting the exterior of said case member and its point extending into said socket en gaging said clamping part and said core face thereby securing said case member to said core and grounding said core.

4. An inductive device comprising .a laminated core, a coil positioned on said core and having avlead, .a metal clamping part secured to one face of said core. and having an indentation formed therein defining a socket with .said core face, a metal case member enclosing said core and said coil and having an opening formed therein in registry with said socket, and a metal connecting member extending through said case member opening into said socket in engagement with said indentation and said core face thereby securing .said case member to said core and grounding said core, said coil lead being clamped between said clamping part and said core face thereby grounding said coil.

5. An inductive device comprising a laminated core, a coil positioned on said core and having a lead, a clamping part formed of relatively thin sheet metal secured to one face of said core and having an indentation formed 20 2,418,531

therein defining a socket with said core face, a metal case member enclosing said core and said coil and having an opening formed therein in registry with said socket, and a metal self-tapping screw arranged in said case member opening with its head abutting the exterior of said case member and its point extending into said socket engaging said clamping part and said core face thereby securing said case member to said core and grounding said core, said coil lead being clamped between said clamping part and said c-ore face thereby grounding said coil.

References Cited in the file of this patent UNITED STATES PATENTS 2,130,243 Mitchell Sept. 13, 1938 2,130,399 Rypinski Sept. 20, 1938 2,173,387 Bale Sept. 19, 1939 2,359,186 Zelt Sept. 26, 1944 2,385,460 Omansky Sept. 25, 1945 Tognola Apr. 8, 1947 

